After much experimentation, I have found that the way to avoid wrinkles is to set the
Fold Resistance and Shear Resistance very high, 50 for fold and 500 for shear,
and Stretch Resistance very low, between 5 and 1, and Stretch Damping to 0.
Also in Collide Against, set Collision Offset and Collision Depth to between
.3 and .4.  If you get too much poke through, bump this up some.